Novel Staphylococcal Cassette Chromosome <i>mec</i> Type, Tentatively Designated Type VIII, Harboring Class A <i>mec</i> and Type 4 <i>ccr</i> Gene Complexes in a Canadian Epidemic Strain of Methicillin-Resistant <i>Staphylococcus aureus</i>
Bibliographic record
Abstract
Staphylococcal cassette chromosome mec (SCCmec) is a mobile genetic element characterized by flanking terminal direct and, in most cases, inverted repeat sequences, the mec and ccr gene complexes, and their surrounding DNA regions. Unique combinations of the mec and ccr gene complexes generate various SCCmec types. Six SCCmec types have been reported to date. We describe here a novel SCCmec type identified in a Canadian methicillin-resistant Staphylococcus aureus (MRSA) epidemic strain. MRSA clinical isolates were screened for known SCCmec types by multiplex and conventional PCR methods. Three phenotypically and genotypically identical MRSA clinical isolates with a pulsotype identical to CMRSA9 were identified locally and found to be nontypeable by available SCCmec typing schemes. Complete sequencing of the SCCmec element revealed a nucleotide fragment of 32,168 bp integrated at an identical chromosomal integration site (attBscc) at the 3' end of the orfX gene. The nucleotide sequences at the chromosome-SCCmec junction regions were typical of other SCCmec types, but the element harbored a unique combination of class A mec and type 4 ccr gene complexes. Sequence recombination analysis suggested that this unique SCCmec type may be derived from homologous recombination between the previously described SCC(RP62A) of S. epidermidis strain RP62A and SCC composite island of S. epidermidis ATCC 12228, respectively, or via recombination of other staphylococcal strains that carry the same or similar mobile cassettes. We identified a previously undescribed type of SCCmec from isolate C10682, tentatively designated type VIII, and we provide compelling evidence supporting the ability of SCC elements to transfer horizontally or undergo recombination to generate new SCCmec types.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".